Congress may not be in charge of making foreign policy, but it sure can influence its implementation. Since taking office in January 2009, members of Congress - drawn primarily but not exclusively from the ranks of the GOP - have slowed the Obama administration's efforts to advance its strategy for dealing with Russia, Syria, Israel, Cuba and a host of other countries. And the midterm elections won't be making things any easier for President Obama.

Republican lawmakers stand to play a huge role in debates next year about the promised July 2011 drawdown of troops in Afghanistan, whether to maintain or increase U.S. foreign assistance packages, and how strongly to press countries such as Russia and China to implement new sanctions against Iran.

If current poll results hold, Republicans will make significant gains in the Senate and probably will take the House, elevating a set of lawmakers to new heights of power and complicating Obama's efforts to execute his foreign policy agenda.

Here's a list of four GOP figures in the House who could be crucial actors on the foreign policy stage when the dust settles after Tuesday's elections.

Eric Cantor

The Virginia congressman, who is the House minority whip, could become majority leader in a GOP-controlled House if Minority Leader John A. Boehner (Ohio) is elected speaker. Cantor, who is particularly active in foreign-policy issues involving Iran and Israel, could see his role expand significantly if he is given the power to set the House floor agenda.

That could spell trouble for the administration's foreign operations budget, which funds the State Department and sets levels for U.S. non-military assistance around the world. Republicans are threatening to withhold aid to countries they think aren't wholly supportive of the United States, and Cantor told the Jewish Telegraph Agency recently that the president's proposed budget might have to be rejected outright if Republicans take power - after separating out U.S. aid for Israel.

Ileana Ros-Lehtinen

If Republicans take the House, Ros-Lehtinen (Fla.) is poised to take over the House Foreign Affairs Committee and could drastically alter the administration's agenda. For example, she is likely to scuttle the drive to ease sanctions and travel restrictions on Cuba, which Chairman Howard L. Berman (D-Calif.) supports. Ros-Lehtinen, who was born in Havana, is an active member of the Cuban American lobby.

Her ascendancy could also spell doom for Berman's bill on foreign-aid reform. She argues often for more vetting of foreign aid in the hope of finding cuts, and she has also introduced legislation to cut U.S. funding for the United Nations and the Palestinian Authority.

A vocal critic of what she considers the Obama team's cool approach to Israeli Prime Minister Binyamin Netanyahu, Ros-Lehtinen could also use the committee as a sounding board for those who want changes in the administration's approach to Middle East peace. "She's no Dick Lugar," said one House aide, referring to her temperate Senate counterpart. "You'll probably see a lot of contentious hearings."

Kay Granger

Although not certain, it's likely that Granger (Tex.) would take over the chairmanship of the House Appropriations subcommittee for State Department and foreign operations if the GOP wins the House. That would give her a large role in writing significant sections of the State Department's funding bill. Although she supported the legislation put forth this year by Chairman Nita M. Lowey (D-N.Y.), she criticized the increases for the foreign-ops budget. She's a strong supporter of a balanced budget amendment, which doesn't bode well for foreign-aid funding.

Granger also serves on the defense subcommittee, placing her at the intersection of the debate over how to balance the national security budget and shift resources from defense to diplomacy and development.

Ed Royce

Royce (Calif.) is symbolic of GOP House members who are active in foreign policy. He could become chairman again of the House Foreign Affairs Terrorism, Nonproliferation, and Trade subcommittee, where his staff could hold hearings on the Middle East, Africa, Afghanistan and any other region sensitive to the administration's national security goals.